JP2012131109A - Method of manufacturing pneumatic tire and bead apex rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability, appearance, and rim deviation-resistance of a bead portion by improving the shape of bead apex rubber.SOLUTION: The method of manufacturing a pneumatic tire 1 includes a connecting step of connecting unvulcanized bead apex rubber 8R to an outer surface 5n of a bead core. An inside surface 9 of the bead apex rubber 8R includes a base 14 extending along the outer surface 5n of the bead core, and a pair of oblique sides 15, 15 extending from both ends of the base 14, respectively, and obliquely in directions separating from the outer surface 5n. A whole width AW of the inside surface is smaller than a width CW of the outer surface 5n of the bead core. The connecting step includes a step of pressing the bead apex rubber 8R against the outer surface 5n of the bead core in order to deform the oblique sides 15 of the inside surface to lay the bead apex rubber along the outer surface 5n of the bead core.

Description

  The present invention improves the shape of the bead apex rubber, prevents the rubber from protruding to the outside in the width direction of the bead core, and improves the durability and aesthetics of the bead part and the resistance to rim displacement. And bead apex rubber.

  As shown in FIG. 1, the pneumatic tire 1 usually extends outward in the tire radial direction from the outer surface 5n in the tire radial direction of the bead core 5 in order to reinforce the bead portion 4 and ensure the tire lateral rigidity. A bead apex rubber 8 made of hard rubber is disposed.

  4 (a) and 4 (b), in a pneumatic tire manufacturing process, the bottom surface d1 of the uncured bead apex rubber d having a triangular cross section is formed on the outer surface c1 of the bead core c. The process of pressing and joining is performed. However, at this step, there is a problem that a part of the bottom side d1 of the bead apex rubber d protrudes to the outside in the width direction of the outer surface c1 of the bead core c. When such a protruding portion e of the bead apex rubber d is incorporated in the tire as it is, as shown in FIG. 4C, an air pocket g is generated between the carcass ply f and the bead core c, and the bead portion b This leads to a decrease in durability. Furthermore, the protruding portion e causes convex portions h that are convex on both sides of the bead portion b in the tire axial direction, thereby deteriorating the aesthetic appearance and anti-rim displacement performance of the bead portion b. Related technologies include the following.

JP 2006-35948 A JP 2000-247119 A

  The present invention has been devised in view of the above problems, and improves the shape of the inner surface of the bead apex rubber facing the outer surface side of the bead core, and its width is smaller than the width of the outer surface of the bead core. Provides a method of manufacturing a pneumatic tire and a bead apex rubber that prevents the bead apex rubber from protruding to the outside in the width direction of the bead core and improves the durability and aesthetics of the bead portion and the resistance to rim displacement. The main purpose is to do.

  The invention according to claim 1 of the present invention is a method for manufacturing a pneumatic tire in which a bead portion is provided with a ring-shaped bead core and a bead apex rubber extending in a tire radial direction from an outer surface of the bead core. A connecting step of connecting the unvulcanized bead apex rubber to the outer surface of the bead core, wherein the bead apex rubber is tapered outwardly from the inner surface facing the outer surface side of the bead core in the tire radial direction. The inner side surface includes a bottom side extending along the outer surface of the bead core and a pair of oblique sides extending in a direction away from the outer surface from both ends of the bottom side, and the total width of the inner side surface is The bead core is smaller than the width of the outer surface, and the connecting step is configured to attach the bead apex rubber to the bead core. By pressing on the outer surface, characterized in that by deforming the hypotenuse of the inner surface comprises the step of along the outer surface of the bead core.

  The invention according to claim 2 is the method for producing a pneumatic tire according to claim 1, wherein the bead core has a substantially rectangular cross section formed by winding steel wires.

  The invention according to claim 3 is the method for producing a pneumatic tire according to claim 1 or 2, wherein the total width AW of the inner surface of the bead apex rubber is 87 to 96% of the width CW of the outer surface of the bead core. .

  According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the width BW of the bottom side of the bead apex rubber is 20 to 50% of the width CW of the outer surface of the bead core. It is a manufacturing method.

  In the invention according to claim 5, the width A along the outer surface of the bead core on the oblique side is 20 to 29% of the width CW of the outer surface of the bead core, and the height B in the direction perpendicular to the outer surface of the bead core on the oblique side is The method for manufacturing a pneumatic tire according to any one of claims 1 to 3, which is 20 to 29% of a width CW of an outer surface of the pneumatic tire.

  The invention according to claim 6 is the method for producing a pneumatic tire according to claim 1, wherein the bead apex rubber is tapered from the inner surface to the tire radial direction outer side.

  The invention according to claim 7 is an unvulcanized bead apex rubber that is used by being connected to the outer surface of the bead core when manufacturing a pneumatic tire, and the bead apex rubber faces the outer surface side of the bead core. The inner side surface extends in a tapered manner from the inner side surface in the tire radial direction, and the inner side surface extends along the outer side of the bead core, and the pair of side walls incline toward the outer side of the bead core from both ends of the base side. It consists of a hypotenuse and the total width of the inner surface is smaller than the width of the outer surface of the bead core.

  In the method for manufacturing a pneumatic tire according to the first aspect, unvulcanized bead apex rubber extending in a tapered shape from the inner surface facing the outer surface side of the bead core to the outer side in the tire radial direction is used. The inner side surface of the bead apex rubber is composed of a bottom side extending along the outer surface of the bead core and a pair of oblique sides extending in a direction away from the outer surface from both ends of the bottom side, and the total width of the inner side surface is It is formed smaller than the width of the outer surface of the bead core. Further, the present invention includes a connecting step of connecting the bead apex rubber to the outer surface of the bead core. In this connecting step, the bead apex rubber is pressed against the outer surface of the bead core, thereby deforming the oblique side of the inner surface to deform the outer surface of the bead core. Including the steps to follow At this time, by defining the shape of the inner side surface of the bead apex rubber as described above, the bead apex rubber is prevented from protruding outside in the width direction of the outer surface of the bead core. Therefore, according to the method for manufacturing a pneumatic tire of the present invention, it is possible to manufacture a pneumatic tire excellent in durability, aesthetics, and rim displacement resistance of the bead portion.

  The bead apex rubber according to claim 7 is tapered from the inner surface facing the outer surface side of the bead core to the outer side in the tire radial direction, the inner surface includes a bottom extending along the outer surface of the bead core, and both ends of the bottom From the pair of oblique sides extending in a direction away from the outer surface, and the entire width of the inner surface is smaller than the width of the outer surface of the bead core. When such a bead apex rubber is connected to the outer surface of the bead core, even if it is pressed against the outer surface of the bead core, it is prevented from protruding outside in the width direction of the outer surface of the bead core. It helps to produce pneumatic tires with excellent rim slip resistance.

It is right side sectional drawing which shows the pneumatic tire obtained by the manufacturing method of this invention. It is the elements on larger scale of a bead core and bead apex rubber. It is the schematic explaining the deformation | transformation aspect at the time of the press of the bead apex rubber of this invention, and a connection process. (A) thru | or (c) are sectional drawings of the bead part of the conventional pneumatic tire.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional view of a pneumatic tire (hereinafter simply referred to as “tire”) 1 obtained by the manufacturing method of the present embodiment. The pneumatic tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. For passenger cars including

  The carcass 6 includes a main body part 6a straddling a pair of bead cores 5 and 5 in a toroidal manner, and a folded part 6b which is continuous from both sides of the main body part 6a and is folded around the bead core 5 from the inner side to the outer side in the tire axial direction. And at least one carcass ply 6A in this embodiment. In the carcass ply 6A, the carcass cord is inclined with respect to the tire equator C direction at an angle of 75 to 90 °, for example. For example, an organic fiber cord or a steel cord is adopted as the carcass cord.

  The belt layer 7 is composed of at least two belt plies 7A and 7B, in the present embodiment, in the tire radial direction, and in the outer two. Each of the belt plies 7A and 7B has a highly elastic belt cord such as a steel cord inclined at an angle of 15 to 40 ° with respect to the tire equator C. The belt plies 7A and 7B are overlapped so that the belt cords cross each other.

  Further, the bead portion 4 is provided with a ring-shaped bead core 5 and a bead apex rubber 8 extending in a taper shape outward from the outer surface 5n of the bead core 5 in the tire radial direction. In the bead portion 4 of the present embodiment, the bead core 5 and the bead apex rubber 8 are disposed between the main body portion 6a and the folded portion 6b of the carcass 6. Thereby, the bending rigidity of the bead part 4 is improved. Moreover, a cord reinforcement layer (not shown) etc. may be arrange | positioned at the bead part 4 as needed. The bead apex rubber 8 has a rubber hardness of, for example, JIS durometer A hardness of preferably 70 degrees or more, more preferably 80 degrees or more, and preferably 95 degrees or less, more preferably 90 degrees or less. .

  Next, the manufacturing method of the pneumatic tire 1 of this embodiment is demonstrated. As shown in FIGS. 2A to 2C, the pneumatic tire manufacturing method of the present embodiment includes a connecting step of connecting an unvulcanized bead apex rubber 8 </ b> R to the outer surface 5 n of the bead core 5.

  As shown in an enlarged view in FIG. 3, the bead core 5 is formed in a ring shape by, for example, winding a single bead wire 11 that has been rubberized in a spiral manner.

  As the bead wire 11, for example, an aromatic polyamide fiber can be adopted in addition to steel such as steel wire.

  The bead core 5 of the present embodiment is formed in a substantially rectangular cross section by winding the bead wires 11 in five rows in the tire axial direction and four steps in the tire radial direction. In such a bead core 5, the outer surface 5 n on the outer side in the tire radial direction is formed by an uneven surface in which recesses 12 between adjacent bead wires 11 and 11 and semicircular arc-shaped protrusions 13 formed by the bead wires 11 are alternately arranged. The Therefore, the outer surface 5n of the bead core 5 of this embodiment can secure a large connection area with the bead apex rubber 8R, and is useful for firmly connecting the two. The bead core 5 may be of a tape bead type in which a tape-like body in which a plurality of bead wires 11 are arranged horizontally is wound in a plurality of layers in addition to a single wind type as in the present embodiment. Further, it may be an integrally formed product of steel without using a bead wire.

  The unvulcanized bead apex rubber 8R is continuously extruded with a predetermined cross-sectional shape using, for example, a well-known rubber extruder (not shown).

  The cross-sectional shape of the bead apex rubber 8R of the present embodiment includes an inner side surface 9 facing the outer surface 5n side of the bead core 5 and a pair of tapered surfaces 10 extending from both ends 9a, 9a of the inner side surface in the tire radial direction. Including.

  The inner side surface 9 is linearly inclined along the outer surface 5n of the bead core in a straight line extending in the width direction of the bead core 5 and from both ends 14a, 14a of the bottom side 14 away from the outer surface 5n of the bead core. It consists of a pair of hypotenuses 15 and 15 extending in the shape. Both the base 14 and the hypotenuse 15 are formed in a straight line. The “outer surface of the bead core” is arranged at both ends in the width direction on the outermost side in the tire radial direction of the bead core 5 when the bead core 5 is formed by winding the bead wire 11 as in this embodiment. The common tangent line n of the outer surfaces of the bead wires 11a and 11b is defined as the outer surface.

  Further, the entire width AW of the inner side surface 9 of the bead apex rubber 8R is formed smaller than the width CW of the outer surface 5n of the bead core 5.

  The bead apex rubber 8 </ b> R having the inner surface 9 as described above is formed in a pentagonal shape having a substantially vertically long cross section including the tapered surface 10.

  In the connecting step, first, as shown in FIG. 2A, the inner side surface 9 of the bead apex rubber 8R is positioned on the outer surface 5n of the bead core 5 formed in advance in another step with the width centers thereof aligned. Placed. Next, for example, a not-shown pressing roller or the like is brought into contact with the tapered surfaces 10 on both sides of the bead apex rubber 8R and pressed toward the bead core (shown in FIG. 2B). As a result, the bead apex rubber 8R is pressed so that the bottom 14 of the inner surface 9 is strongly pressed against the outer surface 5n of the bead core, and the oblique sides 15 on both sides thereof are along the outer surface 5n of the bead core as shown in FIG. The bead apex rubber 8 and the outer surface of the bead core 5 are firmly connected. Moreover, since the entire width AW of the inner side surface 9 is smaller than the width CW of the outer surface 5n of the bead core 5, even if the bead apex rubber 8R is pressed by the bead core 5, the outer side in the width direction of the outer surface 5n of the bead core 5 The protruding portion (shown in FIG. 4) e that protrudes is prevented from being formed. Further, the oblique side 15 extends obliquely from the lower end of the tapered surface 10 (that is, the end portion 9a of the inner surface) to the inner side in the width direction of the outer surface 5n of the bead core 5. The bead apex rubber 8R is deformed so that the hypotenuse 15 extends along the outer surface 5n of the bead core with the end portion 14a of the base 14 as a fulcrum by the above-described pressing, so that the lower end 10a of the tapered surface is formed on the outer surface 5a. It is suppressed from spreading outward in the width direction. That is, the bead apex rubber 8R of the present invention has a smaller outward spread in the width direction of the outer surface 5n of the bead core at the end portion 10a of the tapered surface than the conventional bead apex rubber having a substantially triangular cross section. The protruding portion e is prevented from being formed.

  Thereafter, the carcass ply 6A is folded around the bead core 5 by a process similar to the conventional one, and another rubber member is bonded to form an unvulcanized green tire. And this pneumatic tire is vulcanized and molded to produce the pneumatic tire 1.

  As described above, according to the method for manufacturing a pneumatic tire of the present embodiment, it is possible to prevent the bead apex rubber 8R from overflowing from the outer surface of the bead core 5 and protruding to the side. Therefore, it is possible to prevent as much as possible the occurrence of air accumulation (shown in FIG. 4) g between the bead core 5 and the carcass ply 6A. Therefore, in the pneumatic tire 1 manufactured according to the present invention, the durability of the bead portion 4 is improved. Further, in the tire 1 in which the protruding portion e is not formed, a convex portion (shown in FIG. 4) h in which the bead portion 4 is convex outward in the tire axial direction does not occur. Therefore, the manufacturing method of the pneumatic tire 1 of the present invention can manufacture a pneumatic tire excellent in the beauty of the bead portion 4 and the resistance to rim displacement.

  The bead apex rubber 8R of the present embodiment has a cross-sectional shape that is line-symmetric with respect to a vertical line 14n (shown in FIG. 3) that passes through the center of the base 14. As a result, the hypotenuse 15 of the inner side surface 9 is uniformly deformed and along the outer surface 5n of the bead core in a well-balanced manner. Therefore, the bead apex rubber 8R of this embodiment and the bead core 5 are more firmly connected. However, the left and right hypotenuses 15 can have different lengths and inclination angles.

  The ratio AW / CW between the total width AW of the inner side surface 9 of the bead apex rubber 8R and the width CW of the outer surface 5n of the bead core 5 is preferably limited to a certain range. That is, when the ratio AW / CW is increased, the deformed bead apex rubber 8 may protrude from the outer surface 5 n of the bead core 5. Conversely, when the ratio AW / CW is decreased, the connection area between the inner surface 9 of the bead apex rubber 8R and the outer surface 5n is decreased, and the connection strength between the two may be reduced. From such a viewpoint, the ratio AW / CW is preferably 87% or more, more preferably 90% or more, and preferably 96% or less, more preferably 95% or less.

  Further, the ratio BW / CW between the width BW of the bottom 14 of the bead apex rubber 8R and the width CW of the outer surface 5n of the bead core 5 is preferably limited to a certain range. That is, when the ratio BW / CW increases, the length of the hypotenuse 15 decreases, and the pressed bead apex rubber 8 easily protrudes from the outer surface 5n. On the other hand, when the ratio BW / CW is decreased, the deformation amount of the inner side surface 9 of the bead apex rubber 8R is increased, and the outer surface 5n of the bead core cannot be stably connected, and the durability may be deteriorated. From such a viewpoint, the ratio BW / CW is preferably 20% or more, more preferably 22% or more, and preferably 50% or less, more preferably 45% or less.

  The ratio A / CW of the width A along the outer surface 5n of the bead core of the oblique side 15 and the width CW of the outer surface 5n of the bead core is preferably limited to a certain range. When the ratio A / CW is decreased, the protruding portion e is likely to be generated, so that the durability and appearance of the bead portion 4 and the rim displacement resistance may be deteriorated. On the other hand, when the ratio A / CW increases, a large amount of deformation is required to make the hypotenuse 15 follow the outer surface 5n of the bead core 5, which may cause mold deformation of the bead apex rubber 8R and deteriorate durability. . From such a viewpoint, the ratio A / CW is preferably 20% or more, more preferably 25% or more, and preferably 29% or less, more preferably 27% or less.

  From the same viewpoint, the ratio B / CW of the height B in the direction perpendicular to the outer surface 5n of the bead core on the hypotenuse 15 and the width CW of the outer surface 5n of the bead core is preferably 20% or more, more preferably 25%. The above is desirable, preferably 29% or less, more preferably 27% or less.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.

  In order to confirm the effect of the present invention, an unvulcanized bead apex rubber and a bead core having a cross-sectional shape shown in FIG. And these were connected and pressed, and the test of the amount of rubber protrusion was implemented. All parameters except those shown in Table 1 were the same. The main common specifications are as follows.

Bead apex rubber height H: 45 mm
Rubber hardness after vulcanization of bead apex rubber: 83 degrees Width CW of outer surface of bead core: 7.5 mm
Pressure of bead apex rubber: 150N
Bead wire material: Steel Bead wire diameter φ: 1.2 mm
The test method is as follows.

<Rubber protrusion amount>
The amount of protrusion of the rubber when the inner side surface of the bead apex rubber before vulcanization and the outer surface of the bead core were aligned with each other and the above pressing force was pressed by a pressing roller was measured. The results were evaluated as follows by visual inspection of the operator.
A: The bead apex rubber is press-molded on the outer surface of the bead core in the range of 90 to 100% of the width of the bead core (no protruding portion is generated).
○: 100 to 105% or 85 to 90% of the width of the bead core, and a bead apex rubber is press-molded on the outer surface of the bead core. Table 1 shows the test results.

  Further, a tire for a passenger car having a tire size of 235 / 60R16 having the cross-sectional shape of FIG. 1 and based on the specifications of Table 2 was manufactured using the bead apex rubber and the bead core. And about these, the durability test was implemented as follows. All parameters except those shown in Table 2 were the same. The main common additional specifications are as follows.

<Carcass>
Number of carcass plies: 2 Carcass cord material: Polyester Carcass cord angle: 88 degrees <Belt layer>
Number of belt plies: 2 Ply cord material: Steel Ply cord angle: 20 degrees <Others>
Tire outer diameter: 710.5mm
Tread width: 194mm

<Durability>
Each sample tire is mounted on a rim 16 × 7.0J, and a drum with a diameter of 1.7 m is run for 100 hours at an internal pressure of 180 kPa, a longitudinal load of 15.24 kN, a speed of 60 km / h, and damage that can be visually confirmed occurs in the bead portion. The distance traveled was measured. In addition, it described as 6000 km in the Example which exceeded 6000 km and the damage did not generate | occur | produce.
Table 2 shows the test results.

  As a result of the test, the bead apex rubber of the example does not protrude and is properly fixed to the bead core. Further, in the tire of this example, when A / CW and B / CW were set within a preferable range, the durability was improved, and a significant effect was confirmed.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 4 Bead part 5 Bead core 5n Outer surface 8 of a bead core, 8R Bead apex rubber 9 Inner side surface of bead apex rubber 14 Bottom side of bead apex rubber 15 Oblique side of bead apex rubber

Claims (7)

A method for producing a pneumatic tire in which a bead core is provided with a ring-shaped bead core and a bead apex rubber extending in a tire radial direction from an outer surface of the bead core,
A connection step of connecting the unvulcanized bead apex rubber to the outer surface of the bead core;
The bead apex rubber extends from the inner surface facing the outer surface of the bead core in a tapered shape outward in the tire radial direction,
The inner side surface includes a bottom side extending along the outer surface of the bead core, and a pair of oblique sides extending in a direction away from the outer surface from both ends of the bottom side, and the entire width of the inner side surface is equal to that of the bead core. And smaller than the width of the outer surface,
The connection step includes a step of deforming the oblique side of the inner side surface by pressing the bead apex rubber against the outer surface of the bead core so as to be along the outer surface of the bead core. Method.   The method for producing a pneumatic tire according to claim 1, wherein the bead core has a substantially rectangular cross section formed by winding steel wires.   The method for manufacturing a pneumatic tire according to claim 1 or 2, wherein a total width AW of an inner side surface of the bead apex rubber is 87 to 96% of a width CW of an outer surface of the bead core.   The method for manufacturing a pneumatic tire according to any one of claims 1 to 3, wherein a width BW of the bottom side of the bead apex rubber is 20 to 50% of a width CW of an outer surface of the bead core.   The width A along the outer surface of the bead core on the oblique side is 20 to 29% of the width CW of the outer surface of the bead core, and the height B perpendicular to the outer surface of the bead core on the oblique side is 20 to 29 of the width CW of the outer surface of the bead core. The method for producing a pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is a percentage.   The method for manufacturing a pneumatic tire according to claim 1, wherein the bead apex rubber is tapered from the inner side surface to the outer side in the tire radial direction. When manufacturing a pneumatic tire, an unvulcanized bead apex rubber used by being connected to the outer surface of the bead core,
The bead apex rubber extends from the inner surface facing the outer surface side of the bead core in a tapered shape outward in the tire radial direction,
The inner surface comprises a bottom extending along the outer surface of the bead core, and a pair of oblique sides extending in a direction away from the outer surface of the bead core from both ends of the bottom,
In addition, the bead apex rubber is characterized in that a total width of the inner surface is smaller than a width of the outer surface of the bead core.

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